JPH0697489B2 - Combined type magnetic head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head suitable for recording and reproducing a high frequency signal, and more particularly to a composite magnetic head suitable for a high coercive force recording medium.

[Conventional technology]

In order to meet the demand for higher density magnetic recording, it is advantageous to increase the coercive force of the magnetic recording medium, and in order to record a signal on the magnetic recording medium having a high coercive force, a strong and sharp distribution is required. A magnetic field to have is required. However, since the saturation magnetic flux density of the ferrite material currently used in the magnetic head is about 4500 to 5500 gauss, the strength of the recording magnetic field obtained is limited, and the coercive force of the magnetic recording medium is 10
If it exceeds 00 Oersted, there is insufficient recording. On the other hand, Fe-Al-Si alloy, Ni
Magnetic heads that use crystalline alloys such as -Fe alloys or amorphous alloys such as Co-Nb-Zr alloys are generally superior to ferrite materials in that they have higher saturation magnetic flux density and lower sliding noise. Have characteristics. However, the effective magnetic permeability in the high frequency region of 5 MHz or more is lower than that of ferrite due to eddy current loss when the plate thickness is 10 μm or more, and there is a drawback that the reproduction efficiency becomes low. Further, it is inferior in wear resistance to the ferrite material.

Therefore, in order to solve the above-mentioned drawbacks, there has been proposed a composite magnetic head in which ferrite and a magnetic thin film are combined and the advantages of both are utilized. For example, FIG. 1 is a manufacturing process diagram of a composite magnetic head described in Japanese Patent Laid-Open Publication No. 155513/1983.

In FIG. 1A, first, a groove 3 is formed on a surface 2 parallel to the gap forming surface of the ferrite 1. Next, in (b), a magnetic film 4 having a higher saturation magnetic flux density than ferrite is deposited on the surface 2 parallel to the gap forming surface by sputtering. Next, as shown in (c), the surface 2 parallel to the gap forming surface is ground and polished so that the magnetic thin film 4 remains in the groove 3,
The track width regulating groove 5 is formed as shown in (d). Next, the dash-dotted line portion of (e) is cut off to manufacture the magnetic head core half blocks 6, 6 '. Next, as shown in (f), the magnetic head core half blocks 6 and 6'are joined to form a joined block 7, and the broken line portion is cut to obtain a composite magnetic head 8.

Next, FIG. 2 is a diagram showing a second example of the manufacturing process of the composite type magnetic head, which is described in Japanese Patent Laid-Open Publication No. 155513/1983.

In FIG. 2A, first, a groove 11 is formed on a surface 10 parallel to the gap forming surface of the ferrite 9. Next, in (b), a magnetic thin film 12 having a saturation magnetic flux density higher than that of ferrite is deposited on the surface 10 parallel to the gap forming surface by sputtering. Next, in (c), the glass 13 is filled so as to fill the groove 11.
Melt and adhere. Next, in (d), the gap forming surface 14 is ground and polished. Next, in (e), the winding window groove 15 is formed and cut to cut the magnetic head core half block 1.
6,16 ' Next, as shown in (f) and (g), the magnetic head core half blocks 16 and 16 'are bonded to each other to form a bonded block 17, and the broken line portion is cut to obtain a composite magnetic head 18. .

As described above, in the manufacturing process of the composite magnetic head, a step of forming a groove on the ferrite gap forming surface, applying a magnetic thin film to the groove by spattering, and then polishing and removing the unnecessary magnetic thin film And a step of melting and adhering glass on the magnetic thin film and polishing and removing an unnecessary portion. By the way, as the ferrite of the composite type magnetic head, Mn-Zn ferrite single crystal, which has a high saturation magnetic flux density, a high magnetic permeability and a small sliding noise and has a proven record as a VTR magnetic head, is used. However, the above Mn-Zn
Ferrite single crystal was developed for VTR, and its thermal expansion coefficient is 115-120 × 10 ^-7 / ° C due to the composition of Mn-Zn ferrite single crystal and restrictions of additives. .

[Problems to be solved by the invention]

Thermal expansion coefficient is greater than 120 × 10 ^-7 / ℃ the gap forming surface of the Mn-Zn ferrite single crystal in thermal expansion coefficient 115~120 × 10 ^-7 / ℃ (e.g., Fe-Al-Si alloy 130 to 145 × 10 ^-7 / ℃ or C
o-Nb-Zr type amorphous alloy 130〜140 × 10 ^-7 / ℃) When magnetic thin film is formed by sputtering, the temperature is 350〜4
Since the temperature rises to 50 ° C., stress is generated due to the difference in thermal expansion coefficient during the cooling process after forming the thin film. Therefore, the magnetic thin film may peel off from the ferrite. Further, even if the ferrite substrate is not peeled off, the ferrite substrate warps, so that it is a problem to maintain the dimensional accuracy in the polishing process of the magnetic thin film. Further, the magnetic thin film and the ferrite obtained by the step of polishing and removing the unnecessary magnetic thin film after melting and embedding the glass in the core half and the glass adhered by melting and the step of heating and cooling at the time of joining the ferrite core half The occurrence of cracks, peeling, etc. between them was a problem.

[Means for solving problems]

In order to solve the problems of the composite magnetic head, the present invention is a ferrite having a thermal expansion coefficient of 125 to 145 × 10 ⁻⁷ / ° C. equivalent to that of a magnetic thin film material having a larger saturation magnetic flux density than ferrite. Is used as a magnetic core, and the ferrite has a composition of (MnO, ZnO,
Fe ₂ O ₃ ), expressed as mol% of A (25,16,59), B (25,1
1,64), C (15,14,71), D (15,19,66) are connected by a straight line and may be within a range surrounded by AB, BC, CD and DA.

Further, as the Mn-Zn ferrite, single crystal, polycrystal and fused ferrite can be applied as long as they have the above composition. In the present invention, since the main focus is on the coefficient of thermal expansion of ferrite, the magnetic properties do not necessarily have to be high performance materials. However, for example, the additive applied to the Mn-Zn ferrite single crystal used as a conventional VTR magnetic head for improving the saturation magnetic flux density, magnetic permeability, sliding noise, etc. of the Mn-Zn ferrite single crystal ( For example, Sn
O ₂ , Nb ₂ O ₅ , V ₂ O _5, etc.) may be added. When using polycrystalline Mn-Zn ferrite, additives (eg, CaO, SiO ₂ etc.) may be added for the purpose of controlling the crystal grain boundaries. The density of the sintered body of Mn-Zn ferrite polycrystal is 99
% Or higher density material is preferable.

Furthermore, if the coefficient of thermal expansion is 125 to 145 × 10 ^-7 / ° C, Ni-
It is also possible to use Zn ferrite single crystals, polycrystalline and fused ferrites.

〔Example〕

The Mn-Zn ferrite single crystals of various compositions were grown by the Bridgman method, and the results of composition analysis, including comparative examples,
Shown in the table.

The grown Mn-Zn ferrite single crystal is cut so that the {111} face becomes a gap forming face, the {111} face is mirror-polished, and then cut into a rectangular shape. After that, as shown in FIG. 2 (a), a groove 11 is formed on the {111} plane 10 parallel to the gap forming surface of the rectangular plate 9 of the Mn-Zn ferrite single crystal.

Next, as shown in FIG. 2B, a Fe—Al—Si alloy thin film was formed on the {111} plane 10 parallel to the gap forming surface under the following conditions to a thickness of 3 to 50 μm.

Target diameter: 76mm Input power: 400W Argon pressure: 0.7Pa Substrate temperature: 20 ~ 350 ℃ F after heat treatment at 600 ℃ for 1 hour in nitrogen atmosphere
The presence or absence of peeling of the e-Al-Si alloy thin film was observed. as a result,
No. 1 is indicated by x for peeling and ○ for non-peeling.
Summarized in the table.

Further, the glass 13 is melted and adhered so as to fill the groove 11 as shown in FIG. Next, as in (d), the {111} surface is ground and polished.

In this case, the presence or absence of cracks was observed between the Fe-Al-Si alloy thin film and the Mn-Zn ferrite single crystal substrate. Those with cracks are indicated by x, those without cracks are indicated by o, and are summarized in Table 1.

As shown above, the coefficient of thermal expansion is 125-145 × 10 ^-7 / ℃ Mn-
By using the core made of Zn ferrite single crystal in the composite magnetic head using the Fe-Al-Si alloy thin film, peeling of the magnetic thin film from the ferrite core in the cooling process after thin film formation It is possible to prevent the occurrence of cracks or peeling between the magnetic thin film and the ferrite during the heating / cooling process at the time of joining.

In Table 2, instead of the above Mn-Zn ferrite single crystal, M
The cases of using polycrystalline n-Zn ferrite and fused ferrite are summarized.

As described above, as Mn-Zn ferrite, at least its composition is represented by mol% of (MnO, ZnO, Fe ₂ O ₃ ), and A (25,16,59), B (25,11,64) ), C (15,14,71), D
Single crystal, polycrystal, and fused ferrite are also applicable as long as they are within the range surrounded by AB, BC, CD, and DA in which each point of (15, 19, 66) is connected by a straight line.

Next, a case where a Co—Nb—Zr type amorphous alloy is used as a magnetic thin film in a composite magnetic head will be described.

As the ferrite core, Mn shown in Table 1 and Table 2
-Zn ferrite single crystal and Mn-Zn ferrite polycrystal,
Molten Mn-Zn ferrite was used. As shown in Fig. 2 (b), Co-Nb-Z is formed on the {111} plane 10 parallel to the gap forming plane.
An r-type amorphous alloy thin film was formed in a thickness of 3 to 50 μm under the following conditions.

Target diameter: 126mm Input power: 1kW Argon pressure: 0.5Pa Substrate temperature: 20 to 350 ℃ C after heat treatment at 500 ℃ for 1 hour in nitrogen atmosphere
The presence or absence of peeling of the o-Nb-Zr amorphous alloy film was observed. As a result, those that peel off are marked with X, and those that do not peel off are marked with ○
The results are shown in Table 3 and summarized in Table 3. Further, the glass 13 is melted and adhered so as to fill the groove 11 as shown in FIG.
Next, as in (d), the {111} surface is ground and polished.

In this case, the presence or absence of cracks was observed between the Co-Nb-Zr system amorphous alloy thin film and the Mn-Zn ferrite single crystal substrate. Those with cracks x, those without cracks ○
And is summarized in Table 3.

As the above results show, the coefficient of thermal expansion 125 ~ 145 × 10 ^-7 / ℃ M
By using a core made of n-Zn ferrite single crystal in a composite magnetic head using a Co-Nb-Zr system amorphous alloy thin film, separation of the magnetic thin film from the ferrite core and ferrite in the cooling process after thin film formation It is possible to prevent cracks and peeling between the magnetic thin film and the ferrite from the ferrite core during the heating and cooling process during the joining of the core halves.

In addition, in Table 4, instead of the above Mn-Zn ferrite single crystal, Mn-
The cases of using Zn ferrite polycrystal and fused ferrite are summarized.

As described above, as Mn-Zn ferrite, at least its composition is represented by mol% of (MnO, ZnO, Fe ₂ O ₃ ), and A (25,16,59), B (25,11,64) ), C (15,14,71), D
Within the range enclosed by AB, BC, CD, and DA, which connect each point of (15, 19, 66) with a straight line, that is, its coefficient of thermal expansion is 125 to 145 × 10 ^-7
If it is / ° C, single crystal, polycrystal and fused ferrite can be applied.

FIG. 3 is a characteristic diagram showing the relationship between the composition of Mn-Zn ferrite and the coefficient of thermal expansion. The shaded area is the area suitable for the present invention.

〔The invention's effect〕

According to the present invention, in the manufacturing process of the composite magnetic head, it is possible to prevent the separation between the magnetic thin film and the ferrite, the generation of cracks, and the like, so that the composite magnetic head can be stably manufactured.

[Brief description of drawings]

1 and 2 are views for explaining a method of manufacturing a composite magnetic head, and FIG. 3 is a view for explaining an embodiment of the present invention. 2 ... Ferrite substrate, 3 ... Groove, 4 ... Magnetic thin film, 6
…… Core half block, 10 …… Ferrite substrate, 11 ……
Groove, 12 ... Magnetic thin film, 15 ... Winding window groove.

Claims (2)

[Claims] 1. A magnetic metal half having a saturation magnetic flux density higher than that of the ferrite, wherein magnetic core halves made of a pair of ferrites are arranged so as to face each other with a magnetic gap interposed therebetween, and at least one magnetic core half has a facing portion. In the composite magnetic head having a thin film layer formed, the main composition of the above ferrite is represented by at least (MnO, ZnO, Fe ₂ O ₃ ) mol%, and A (25, 16, 5
9), B (25,11,64), C (15,14,71), D (15,19,66) within the range enclosed by AB, BC, CD and DA that connect each point with a straight line In addition, the coefficient of thermal expansion of the above ferrite is 125 ~ 145x10
A composite magnetic head characterized in that the temperature is ^-7 / ° C. 2. The composite magnetic head according to claim 1, wherein the ferrite is a single crystal of Mn-Zn ferrite.